Golf Balls having a Casing Layer Formed from a Single High Acid Based Ionomer with an Ultra High Melt Flow Index Maleic Anhydride Terpolymer

ABSTRACT

The present invention is a multi-piece golf ball having a casing layer comprising of a single high acid based ionomer that is blended with an ultra high melt flow index maleic anhydride terpolymer with a melt flow index of at least 70 g/10 min. at 190° C. The maleic anhydride terpolymer comprises a copolymer of ethylene-alkyl acrylate-maleic anhdydride. The alkyl acrylate is selected from methyl, or ethyl, or propyl, or butyl, or pentyl acrylate. The maleic anhydride content in the terpolymer is 1 to 4% of the total blend by weight. The single high acid ionomer such as a copolymer of ethylene-acrylic or methacrylic is partially neutralized with a suitable cation such as lithium, sodium, magnesium, zinc, or potassium.

FIELD OF THE INVENTION

The present invention is directed to multi-piece golf balls having a casing layer comprising of a single high acid based ionomer that is blended with an ultra high melt flow index maleic anhydride terpolymer.

BACKGROUND OF THE INVENTION

Conventional golf balls can be divided into two general groups: solid balls or wound balls. The difference in playing characteristics resulting from these different types of construction can be significant. Balls having a solid construction are popular with golfers because they provide durability and maximum distance. Solid balls are generally made with a solid core, usually made of a cross linked rubber, enclosed by a cover material. Typically, the solid core is made of polybutadiene crosslinked with zinc diacrylate and/or similar crosslinking agents. Solid cores may also contain a number of layers. The cover is generally an ionomeric material, such as SURLYN®, which is a tradename for a family of ionomer resins produced by E. I. DuPont de Nemours & Co. of Wilmington, Del. Covers may include one or more layers.

The combination of the solid core and ionomeric cover materials provide a ball that is durable and abrasion resistant. However, because these materials are rigid, solid balls can have a hard “feel” when struck with a club. Also, due to their construction, these balls tend to have a relatively lower spin rate and higher initial velocity, which can provide greater distance and increased accuracy off the tee but less control for greenside play.

Recently, manufacturers have investigated the use of alternative polymers, such as polyurethane, for use as golf ball covers. For example, U.S. Pat. No. 6,132,324, incorporated herein by reference, discloses a method of making a golf ball having a polyurethane cover. Polyurethanes have been recognized as useful materials for golf balls since about 1960. Polyurethane compositions are the product of a reaction between a curing agent and a polyurethane prepolymer, which is itself a product formed by a reaction between a polyahl and an isocyanate. As disclosed in U.S. Pat. No. 4,594,364 to Pawloski, et al., “polyahl” includes any organic compound having at least two active hydrogen moieties and an average molecular weight of at least 62. Typical polyahls include polyols, polyamines, polyamides, polymercaptans, polyacids, and the like. The curing agents used previously are typically diamines or polyols. A catalyst is often employed to promote the reaction between the curing agent and the polyurethane prepolymer.

The first commercially successful polyurethane covered golf ball was the Titleist Professional ball, first released in 1993. Subsequently, the Titleist Pro-V1 ball was introduced successfully in 2000 with a solid resilient polybutadiene core, a hard ionomer casing and a polyurethane cover. The Pro-V1 ball provided both professional and amateur players with long distance off of drivers and control for greenside play.

The composition of the hard ionomer casing layers is important in determining the ball's spin rate and controllability. These casing layers often are made using soft or hard ionomeric resins, elastomeric resins, or blends of these, similar to those used in cover layers. Examples of polymer blend compositions for casing layers are described in a number of patents, including U.S. Pat. No. 6,355,715 to Ladd, which describes a casing layer comprising polyether-type polyurethane and a second thermoplastic component, such as a block copolymer, dynamically vulcanized thermoplastic elastomer, or other listed components. Also, U.S. Pat. No. 5,253,871 to Viollaz describes layer compositions incorporating amide block copolyether and ionomer, and U.S. Pat. No. 6,124,389 to Cavallaro et al. describes intermediate layer compositions incorporating an ethylene methacrylic/acrylic acid copolymer and other specified thermoplastic components.

Recently, Fusabond® 525D which is a tradename for a maleic anhydride modified metallocene catalyzed ethylene-butene copolymers, produced by E. I. DuPont de Nemours & Co. of Wilmington, Del. has been introduced for use in golf ball cover layers. Fusabond® has been successful in increasing the toughness of filled, reinforced or blended polymer compounds. However, efforts to utilize Fusabond® in the casing layer of golf balls has met with some resistance due to the inherent low melt flow index of the Fusabond® which is only about 3.5 g/10 min at 190° C. Casing layer formulations have had a tendency to experience a processing difficulty with the relatively low melt index ranging from 0.4 to 1.6 g/10 minutes at 190° C. (ASTM D-1238)for a 24% to 16.5% Fusabond® concentration. This has caused a huge hurdle in the use of Fusabond® in the casing layer molding process, especially in retractable injection molding processes (wherein difficulty is in filling the mold), as well as in compression molding processes where there is a requirement that the molding be at a much higher temperature (over 300° F.) than with other conventional materials.

There is a need to replace low melt flow compositions such as Fusabond® 525 D with high melt flow compositions that will perform equally as well as golf balls having ionomer casings, yet will have improved processability.

SUMMARY OF THE INVENTION

In one embodiment, the present invention is directed to a golf ball comprising a core, at least one casing layer and a cover, wherein the casing layer is formed from an ultra high melt flow index maleic anhydride terpolymer having a melt flow index of at least 70 g/10 min. at 190° C. blended with a single high acid based ionomer. A melt flow index preferably is at least about 70 to 225 g/10 min. at 190° C., and more preferably is at least about 175 g/10 min. at 190° C.

The maleic anhydride terpolymer comprises a terpolymer of ethylene-alkyl acrylate-maleic anhydride. The alkyl acrylate is selected from methyl, or ethyl, or propyl, or butyl, or pentyl or hexyl or octyl acrylate. The maleic anhydride level in the terpolymer is preferably about 1 to 4 wt %, more preferably about 2 to 3 wt %, and most preferably about 2.5 to 3.0 wt % of the total blend by weight.

One embodiment employs a single high acid ionomer of either ethylene-acrylic or methacrylic acid neutralized with a cation such as lithium, sodium, magnesium, zinc, or potassium, wherein the acid content is preferably from about 16 to 25% by weight, more preferably from about 17 to 22% by weight, and most preferably from about 17 to 19% by weight.

An embodiment of the invention neutralizes the ionomer to a level of about 30 to 70% by weight. The melt flow index of the ionomer is preferably about 1 to 5 g/10 min. at 190° C. more preferably about 2 to 4.5 g/10 min. at 190° C., and most preferably from about 2.5 to 4.5 g/10 min. at 190° C.

In one embodiment of the invention, the maleic anhydride terpolymer used in the casing composition is preferably about 10 to 40% by weight, more preferably about 15 to 30% by weight, and most preferably 16 to 25% by weight.

DETAILED DESCRIPTION OF THE INVENTION

The golf ball of the present invention provides a substitute for the high acid Fusabond in the casing layers of golf balls. Fusabond® is a tradename for a family of resins produced by E. I. DuPont de Nemours & Co. of Wilmington, Del. The inherent low melt flow index of the Fusabond® 525D (about 3.5 g/10 min. at 100° C.) when combined with an ionomer such as Surlyn® 8150, causes the casings to have a low melt flow index ranging from 0.4 to 1.80 g/10 min at 190° C. for a 24 wt % to 16.5 wt % Fusabond concentration. This creates severe molding process problems, especially with retractable injection or compression molding of the casing layer.

Golf balls of the present invention, which are inherently multi-piece golf balls, have a casing layer (inner cover) formed from ultra high melt flow index maleic anhydride terpolymers (having a melt flow index of at least 10 g/10 min at 190° C., preferably 20 to 250 g/10 min. and more preferably 70 to 225 g/10 min. at 190° C. and most preferably 175 to 225 g/10 min. at 190° C.). The maleic anhydride terpolymer has a melting point in the range of 65 to 108° C., and preferably a melting point in the range of 100 to 102° C. The melting point was measured using a different scanning calorimetric method at a heating rate of 10° C./min. The flexural modulus of the maleic anhydride terpolymer is in the range of 1,000 to 20,000 psi and more preferably in the range of 6,000 to 8000 psi. These may comprise such combinations as ethylene or propylene; a methyl, or propyl, or butyl, or pentyl acrylate; and a maleic anhydride to form a terpolymer that is blended with a single high acid based ionomer to provide a composition having improved processability yet still retaining superior golf ball properties. When the maleic anhydride terpolymer comprises a copolymer of ethylene-alkyl acrylate-maleic anhydride, the alkyl acrylate ay be ethyl acrylate having a 5 to 10 weight percent in the terpolymer. The maleic anhydride in the terpolymer is from 1 to 4 wt %, and preferably from 2.5 to 3.0 wt %.

Golf balls for the present invention were developed by the following method: an ultra high flow maleic anhydride terpolymer was twin-screw extruded with a single high acid ionomer (Surlyn® 8150) optionally in the presence of additional melt flow modifiers such as ethylene-acrylic or methacrylic acid copolymers having a melt flow index of 60 to 1500. The twin-screw pellets were injection molded by Reaction Injection Molding Process (RPIM) to produce a casing layer and the experimental formulations of the present invention are represented by Groups 1 through 4 in Table 1 below. In the examples of Table 1, the Fusabond® 525D is replaced by various concentrations of Lotader® 8200 (a tradename for a family of maleic anhydride modified ethylene polymers, produced by Arkema Inc. of Philadelphia, Pa.). The resulting compositions appear to have much improved melt flow indexes over Groups 5 and 6, which represent those casings using Fusabond 572D in their formulations, and this increased melt flow is achieved without sacrificing performance properties.

TABLE 1 Casings Evaluation: Effect of Ultra high melt flow index maleic anhydride terpolymer Group 5 Group 1 Group 2 Group 3 Group 4 (Control) (wt %) (wt %) (wt %) (wt %) (wt %) Group 6 Surlyn 8150 86 81 76 71 72 72 Fusabond 525D 24 24 Nucrel ® 960 4 4 4 4 4 Lotader ® 8200 10 15 20 25 Primacor ® 59901 4 Melt flow Index, g./10 min 4.30 4.75 4.71 4.72 1.00 1.74 @230° C./2.16 kg load PHYSICAL/PERFORMANCE on CASINGS Average Diameter, (in) 1.621 1.623 1.623 1.623 1.622 1.622 Weight (oz) 1.465 1.468 1.467 1.466 1.464 1.465 Hardness (Shore D) 65 63.6 61.8 60.9 59.2 59.9 Hardness (Shore C) 92.8 92.4 91 89.9 87.4 88 CoR@125 ft/sec 0.804 0.802 0.800 0.799 0.799 0.800

One embodiment employs a single high acid ionomer of either ethylene-acrylic or methacrylic acid neutralized with a cation such as lithium, sodium, magnesium, zinc, or potassium, wherein the acid content is preferably from about 16 to 25% by weight, more preferably from about 17 to 22% by weight, and most preferably from about 17 to 19% by weight.

An embodiment of the invention neutralizes the ionomer to a level of about 30 to 70% by weight. The melt flow index of the ionomer is preferably about 1 to 5 g/10 min. at 190° more preferably about 2 to 4.5 g/10 min. at 190°, and most preferably from about 2.5 to 4.5 g/10 min. at 190°. It is to be appreciated that the ionomer could also be fully neutralized to a level between 75 to 100%.

In one embodiment of the invention, the maleic anhydride terpolymer present in the casing layer is preferably about 10 to 40% by weight, more preferably about 15 to 30% by weight, and most preferably 16 to 25% by weight, with the casing layer having a thickness of 0.030 to 0.050 inch.

For purposes of the present disclosure, material hardness is measured according to ASTM D2240 and generally involves measuring the hardness of a flat “slab” or “button” formed of the material. It should be understood that there is a fundamental difference between “material hardness” and “hardness as measured directly on a golf ball.” Hardness as measured directly on a golf ball (or other spherical surface) typically results in a different hardness value than material hardness. This difference in hardness values is due to several factors including, but not limited to, ball construction (i.e., core type, number of core and/or cover layers, etc.), ball (or sphere) diameter, and the material composition of adjacent layers. It should also be understood that the two measurement techniques are not linearly related and, therefore, one hardness value cannot easily be correlated to the other. Unless stated otherwise, the hardness values given herein for cover materials, including inner cover layer materials and outer cover layer materials, are material hardness values measured according to ASTM D2240, with all values reported following 10 days of aging at 50% relative humidity and 23° C.

The surface hardness of a golf ball layer is obtained from the average of a number of measurements taken from opposing hemispheres, taking care to avoid making measurements on the parting line of the core or on surface defects, such as holes or protrusions. Hardness measurements are made pursuant to ASTM D-2240 “Indentation Hardness of Rubber and Plastic by Means of a Durometer.” Because of the curved surface, care must be taken to insure that the golf ball or golf ball subassembly is centered under the durometer indentor before a surface hardness reading is obtained. A calibrated, digital durometer, capable of reading to 0.1 hardness units is used for all hardness measurements and is set to take hardness readings at 1 second after the maximum reading is obtained. The digital durometer must be attached to, and its foot made parallel to, the base of an automatic stand, such that the weight on the durometer and attack rate conform to ASTM D-2240.

The center hardness of a core is obtained according to the following procedure. The core is gently pressed into a hemispherical holder having an internal diameter approximately slightly smaller than the diameter of the core, such that the core is held in place in the hemispherical portion of the holder while concurrently leaving the geometric central plane of the core exposed. The core is secured in the holder by friction, such that it will not move during the cutting and grinding steps, but the friction is not so excessive that distortion of the natural shape of the core would result. The core is secured such that the parting line of the core is roughly parallel to the top of the holder. The diameter of the core is measured 90 degrees to this orientation prior to securing. A measurement is also made from the bottom of the holder to the top of the core to provide a reference point for future calculations. A rough cut is made slightly above the exposed geometric center of the core using a band saw or other appropriate cutting tool, making sure that the core does not move in the holder during this step. The remainder of the core, still in the holder, is secured to the base plate of a surface grinding machine. The exposed ‘rough’ surface is ground to a smooth, flat surface, revealing the geometric center of the core, which can be verified by measuring the height of the bottom of the holder to the exposed surface of the core, making sure that exactly half of the original height of the core, as measured above, has been removed to within ±0.004 inches. Leaving the core in the holder, the center of the core is found with a center square and carefully marked and the hardness is measured at the center mark.

Golf ball cores of the present invention may have a zero or negative or positive hardness gradient. A hardness gradient is defined by hardness measurements made at the surface of the layer (e.g., center, outer core layer, etc.) and radially inward towards the center of the ball, typically at 2 mm increments. For purposes of the present invention, “negative” and “positive” refer to the result of subtracting the hardness value at the innermost portion of the golf ball component from the hardness value at the outer surface of the component. For example, if the outer surface of a solid core has a lower hardness value than the center (i.e., the surface is softer than the center), the hardness gradient will be deemed a “negative” gradient. In measuring the hardness gradient of a core, the center hardness is first determined according to the procedure above for obtaining the center hardness of a core. Once the center of the core is marked and the hardness thereof is determined, hardness measurements at any distance from the center of the core may be measured by drawing a line radially outward from the center mark, and measuring and marking the distance from the center, typically in 2 mm increments. All hardness measurements performed on a plane passing through the geometric center are performed while the core is still in the holder and without having disturbed its orientation, such that the test surface is constantly parallel to the bottom of the holder. The hardness difference from any predetermined location on the core is calculated as the average surface hardness minus the hardness at the appropriate reference point, e.g., at the center of the core for a single, solid core, such that a core surface softer than its center will have a negative hardness gradient. Hardness gradients are disclosed more fully, for example, in U.S. patent application Ser. No. 11/832,163, filed on Aug. 1, 2007; Ser. No. 11/939,632, filed on Nov. 14, 2007; Ser. No. 11/939,634, filed on Nov. 14, 2007; Ser. No. 11/939,635, filed on Nov. 14, 2007; and Ser. No. 11/939,637, filed on Nov. 14, 2007; the entire disclosure of each of these references is hereby incorporated herein by reference.

Golf ball cores of the present invention typically have an overall core compression of less than 110, or a compression of 100 or less, or an overall core compression within a range having a lower limit of 20 or 50 or 60 or 65 or 70 or 75 and an upper limit of 80 or 85 or 90 or 100 or 110 or 120, or an overall core compression of about 80. Compression is an important factor in golf ball design. For example, the compression of the core can affect the ball's spin rate off the driver and the feel. As disclosed in Jeff Dalton's Compression by Any Other Name, Science and Golf IV, Proceedings of the World Scientific Congress of Golf (Eric Thain ed., Routledge, 2002) (“J. Dalton”), several different methods can be used to measure compression, including Atti compression, Riehle compression, load/deflection measurements at a variety of fixed loads and offsets, and effective modulus. For purposes of the present invention, “compression” refers to Atti compression and is measured according to a known procedure, using an Atti compression test device, wherein a piston is used to compress a ball against a spring. The travel of the piston is fixed and the deflection of the spring is measured. The measurement of the deflection of the spring does not begin with its contact with the ball; rather, there is an offset of approximately the first 1.25 mm (0.05 inches) of the spring's deflection. Very low stiffness cores will not cause the spring to deflect by more than 1.25 mm and therefore have a zero compression measurement. The Atti compression tester is designed to measure objects having a diameter of 42.7 mm (1.68 inches); thus, smaller objects, such as golf ball cores, must be shimmed to a total height of 42.7 mm to obtain an accurate reading. Conversion from Atti compression to Riehle (cores), Riehle (balls), 100 kg deflection, 130-10 kg deflection or effective modulus can be carried out according to the formulas given in J. Dalton.

Golf ball cores of the present invention typically have a coefficient of restitution (“COR”) at 125 ft/s of at least 0.75, preferably at least 0.78, and more preferably at least 0.79. COR, as used herein, is determined according to a known procedure wherein a golf ball or golf ball subassembly (e.g., a golf ball core) is shot from an air cannon at a given velocity (125 ft/s for purposes of the present invention). Ballistic light screens are located between the air cannon and the steel plate to measure ball velocity. As the ball travels toward the steel plate, it activates each light screen, and the time at each light screen is measured. This provides an incoming transit time period proportional to the ball's incoming velocity. The ball impacts the steel plate and rebounds though the light screens, which again measure the time period required to transit between the light screens. This provides an outgoing transit time period proportional to the ball's outgoing velocity. COR is then calculated as the ratio of the outgoing transit time period to the incoming transit time period, COR=T_(out)/T_(in).

Cores of the present invention are enclosed with a cover, which may be a single-, dual-, or multi-layer cover. The golf ball core may be a hollow, a liquid filled or wound core known in the golf ball art.

Suitable cover layer materials for the golf balls disclosed herein include, but are not limited to, ionomer resin and blends thereof (particularly Surlyn® ionomer resins), polyurethanes, polyureas, (meth)acrylic acid, thermoplastic rubber polymers, thermoplastic elastomers, dynamically vulcanized elastomers, polyethylene, and synthetic or natural vulcanized rubber, such as balata. Suitable commercially available ionomeric cover materials include, but are not limited to, Surlyn® ionomer resins and DuPont® HPF 1000 and HPF 2000, commercially available from E. I. du Pont de Nemours and Company; Iotek® ionomers, commercially available from ExxonMobil Chemical Company and Clarixe ionomers, commercially available from A. Schulman.

Particularly suitable outer cover layer materials include relatively soft polyurethanes and polyureas, and having preferred thicknesses of 0.025 to 0.045 inches. When used as cover layer materials, polyurethanes and polyureas can be thermoset or thermoplastic. Thermoset materials can be formed into golf ball layers by conventional casting or reaction injection molding techniques. Thermoplastic materials can be formed into golf ball layers by conventional compression or injection molding techniques. Light stable polyureas and polyurethanes are preferred for the outer cover layer material. In embodiments of the present invention wherein a golf ball having a single layer cover is provided, the cover layer material is preferably selected from polyurethane and polyurea. In embodiments of the present invention wherein a golf ball having a dual cover is provided, the inner cover layer is preferably a high modulus thermoplastic, and the outer cover layer is preferably selected from polyurethane and polyurea.

Suitable cover layer materials also include blends of ionomers with thermoplastic elastomers. Suitable ionomeric cover materials are further disclosed, for example, in U.S. Pat. Nos. 6,653,382, 6,756,436, 6,894,098, 6,919,393, and 6,953,820, the entire disclosures of which are hereby incorporated by reference. Suitable polyurethane cover materials are further disclosed in U.S. Pat. Nos. 5,334,673, 6,506,851, 6,756,436, and 7,105,623, the entire disclosures of which are hereby incorporated herein by reference. Suitable polyurea cover materials are further disclosed in U.S. Pat. Nos. 5,484,870 and 6,835,794, the entire disclosures of which are hereby incorporated herein by reference. Suitable polyurethane-urea hybrids are blends or copolymers comprising urethane or urea segments as disclosed in U.S. Patent Application Publication No. 2007/0117923, the entire disclosure of which is hereby incorporated herein by reference. Additional suitable cover materials are disclosed, for example, in U.S. Patent Application Publication No. 2005/0164810, U.S. Pat. No. 5,919,100, and PCT Publications WO00/23519 and WO00/29129, the entire disclosures of which are hereby incorporated herein by reference.

The inner cover layer material may include a flow modifier, such as, but not limited to, Nucrel® acid copolymer resins, and particularly Nucrel® 960. Nucrel® acid copolymer resins are commercially available from E. I. du Pont de Nemours and Company.

The outer cover layer is preferably formed from a composition comprising polyurethane, polyurea, or a copolymer or hybrid of polyurethane/polyurea. The outer cover layer material may be thermoplastic or thermoset.

In a particular embodiment, the cover is a single layer preferably formed from an ionomeric composition. The single layer cover preferably has a surface hardness of 65 Shore D or less, or 60 Shore D or less, or 45 Shore D or less, or 40 Shore D or less, or from 25 Shore D to 40 Shore D, or from 30 Shore D to 40 Shore D and a thickness within a range having a lower limit of 0.010 or 0.015 or 0.020 or 0.025 or 0.030 or 0.055 or 0.060 inches and an upper limit of 0.065 or 0.080 or 0.090 or 0.100 or 0.110 or 0.120 or 0.140 inches. The flexural modulus of the cover, as measured by ASTM D6272-98 Procedure B, is preferably 500 psi or greater, or from 500 psi to 150,000 psi, more preferably from 10,000 to 45,000 psi and most preferably from 15,000 to 35,000 psi.

In another particular embodiment, the cover is a two-layer cover consisting of a casing layer and a cover. The casing layer is preferably formed from an ionomeric composition and preferably has a surface hardness of 60 Shore D or greater, or a surface hardness within a range having a lower limit of 30 or 40 or 55 or 60 or 65 Shore D and an upper limit of 66 or 68 or 70 or 75 Shore D, and a thickness within a range having a lower limit of 0.010 or 0.015 or 0.020 or 0.030 inches and an upper limit of 0.035 or 0.040 or 0.045 or 0.050 or 0.055 or 0.075 or 0.080 or 0.100 or 0.110 or 0.120 inches. The casing layer composition preferably has a material hardness of 95 Shore C or less, or less than 95 Shore C, or 92 Shore C or less, or 90 Shore C or less, or has a material hardness within a range having a lower limit of 70 or 75 or 80 or 84 or 85 Shore C and an upper limit of 90 or 92 or 95 Shore C. The cover is preferably formed from a castable or reaction injection moldable polyurethane, polyurea, or copolymer or hybrid of polyurethane/polyurea. Such cover material is preferably thermosetting, but may be thermoplastic. The cover composition preferably has a material hardness of 85 Shore C or less, or 45 Shore D or less, or 40 Shore D or less, or from 25 Shore D to 40 Shore D, or from 30 Shore D to 40 Shore D. The cover preferably has a surface hardness within a range having a lower limit of 20 or 30 or 35 or 40 Shore D and an upper limit of 52 or 58 or 60 or 65 or 70 or 72 or 75 Shore D. The cover preferably has a thickness within a range having a lower limit of 0.010 or 0.015 or 0.025 inches and an upper limit of 0.035 or 0.040 or 0.045 or 0.050 or 0.055 or 0.075 or 0.080 or 0.115 inches. The two-layer cover preferably has an overall thickness within a range having a lower limit of 0.010 or 0.015 or 0.020 or 0.025 or 0.030 or 0.055 or 0.060 inches and an upper limit of 0.065 or 0.075 or 0.080 or 0.090 or 0.100 or 0.110 or 0.120 or 0.140 inches.

The present invention is not limited by any particular process for forming the golf ball layer(s). It should be understood that the layer(s) can be formed by any suitable technique, including injection molding, compression molding, casting, and reaction injection molding.

When injection molding is used, the composition is typically in a pelletized or granulated form that can be easily fed into the throat of an injection molding machine wherein it is melted and conveyed via a screw in a heated barrel at temperatures of from 150° F. to 600° F., preferably from 200° F. to 500° F. The molten composition is ultimately injected into a closed mold cavity, which may be cooled, at ambient or at an elevated temperature, but typically the mold is cooled to a temperature of from 50° F. to 70° F. After residing in the closed mold for a time of from 1 second to 300 seconds, preferably from 20 seconds to 120 seconds, the core and/or core plus one or more additional core or cover layers is removed from the mold and either allowed to cool at ambient or reduced temperatures or is placed in a cooling fluid such as water, ice water, dry ice in a solvent, or the like.

When compression molding is used to form a center, the composition is first formed into a preform or slug of material, typically in a cylindrical or roughly spherical shape at a weight slightly greater than the desired weight of the molded core. Prior to this step, the composition may be first extruded or otherwise melted and forced through a die after which it is cut into a cylindrical preform. It is that preform that is then placed into a compression mold cavity and compressed at a mold temperature of from 150° F. to 400° F., preferably from 250° F. to 350° F., and more preferably from 260° F. to 295° F. When compression molding a core or cover of an HNP composition, a half-shell is first formed via injection molding and then a core comprising one or more layers is enclosed within two half shells and then compression molded in a similar manner to the process previously described.

Reaction injection molding processes are further disclosed, for example, in U.S. Pat. Nos. 6,083,119, 7,338,391, 7,282,169, 7,281,997 and U.S. Patent Application Publication No. 2006/0247073, the entire disclosures of which are hereby incorporated herein by reference.

The compositions of the invention can be used with a variety of golf ball constructions. For example, the compositions of the invention may be used as a cover layer in a two-piece ball with a large core, an outer cover layer in a three piece ball with a relatively thin inner cover layer, an intermediate layer in a three-piece ball, or an inner cover layer in a golf ball having dual cover layers. In addition, the compositions of the invention may be used in cores of golf balls having outer components formed from castable reactive liquid materials or injection moldable thermoplastic materials.

Golf balls of the present invention typically have a compression of 120 or less, or a compression within a range having a lower limit of 40 or 50 or 60 or 65 or 75 or 80 or9O and an upper limit of95 or 100 or 105 or 110 or 115 or 120. Golf balls of the present invention typically have a COR at 125 ft/s of at least 0.75, preferably at least 0.78, and more preferably at least 0.79.

Golf balls of the present invention will typically have dimple coverage of 60% or greater, preferably 65% or greater, and more preferably 75% or greater. The United States Golf Association specifications limit the minimum size of a competition golf ball to 1.680 inches. There is no specification as to the maximum diameter, and golf balls of any size can be used for recreational play. Golf balls of the present invention can have an overall diameter of any size. The preferred diameter of the present golf balls is from 1.680 inches to 1.800 inches. More preferably, the present golf balls have an overall diameter of from 1.680 inches to 1.760 inches, and even more preferably from 1.680 inches to 1.740 inches.

Golf balls of the present invention preferably have a moment of inertia (“MOI”) of 70-95 g·cm², preferably 75-93 g·cm², and more preferably 76-90 g·cm². For low MOI embodiments, the golf ball preferably has an MOI of 85 g·cm² or less, or 83 g·cm² or less. For high MOI embodiment, the golf ball preferably has an MOI of 86 g·cm² or greater, or 87 g·cm² or greater. MOI is measured on a model MOI-005-104 Moment of Inertia Instrument manufactured by Inertia Dynamics of Collinsville, Conn. The instrument is connected to a PC for communication via a COMM port and is driven by MOI Instrument Software version #1.2.

Thermoplastic layers herein may be treated in such a manner as to create a positive or negative hardness gradient. In golf ball layers of the present invention wherein a thermosetting rubber is used, gradient-producing processes and/or gradient-producing rubber formulation may be employed. Gradient-producing processes and formulations are disclosed more fully, for example, in U.S. patent application Ser. No. 12/048,665, filed on Mar. 14, 2008; Ser. No. 11/829,461, filed on Jul. 27, 2007; Ser. No. 11/772,903, filed Jul. 3, 2007; Ser. No. 11/832,163, filed Aug. 1, 2007; Ser. No. 11/832,197, filed on Aug. 1, 2007; the entire disclosure of each of these references is hereby incorporated herein by reference.

In addition to the materials disclosed above, any of the core or cover layers may comprise one or more of the following materials: thermoplastic elastomer, thermoset elastomer, synthetic rubber, thermoplastic vulcanized polymers, copolymeric ionomer, terpolymeric ionomer, polycarbonate, polyolefin, polyamide, copolymeric polyamide, polyesters, polyester-amides, polyether-amides, polyvinyl alcohols, acrylonitrile-butadiene-styrene copolymers, polyarylate, polyacrylate, polyphenylene ether, impact-modified polyphenylene ether, high impact polystyrene, metallocene-catalyzed polymers, styrene-acrylonitrile (SAN), olefin-modified SAN, acrylonitrile-styrene-acrylonitrile, styrene-maleic anhydride (S/MA) polymer, styrenic copolymer, functionalized styrenic copolymer, functionalized styrenic terpolymer, styrenic terpolymer, cellulose polymer, liquid crystal polymer (LCP), ethylene-propylene-diene rubber (EPDM), ethylene-vinyl acetate copolymer (EVA), ethylene propylene rubber (EPR), ethylene vinyl acetate, polyurea, and polysiloxane. Suitable polyamides for use as an additional material in compositions disclosed herein also include resins obtained by: (1) polycondensation of (a) a dicarboxylic acid, such as oxalic acid, adipic acid, sebacic acid, terephthalic acid, isophthalic acid or 1,4-cyclohexanedicarboxylic acid, with (b) a diamine, such as ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, or decamethylenediamine, 1,4-cyclohexyldiamine or m-xylylenediamine; (2) a ring-opening polymerization of cyclic lactam, such as ε-caprolactam or ω-laurolactam; (3) polycondensation of an aminocarboxylic acid, such as 6-aminocaproic acid, 9-aminononanoic acid, 11-aminoundecanoic acid or 12-aminododecanoic acid; or (4) copolymerzation of a cyclic lactam with a dicarboxylic acid and a diamine. Specific examples of suitable polyamides include Nylon 6, Nylon 66, Nylon 610, Nylon 11, Nylon 12, copolymerized Nylon, Nylon MXD6, and Nylon 46.

In embodiments of the present invention wherein at least one layer is formed from a rubber composition, suitable rubber compositions include natural and synthetic rubbers, including, but not limited to, polybutadiene, polyisoprene, ethylene propylene rubber (“EPR”), ethylene propylene diene rubber (“EPDM”), styrenic block copolymer rubbers (such as Si, SIS, SB, SBS, SIBS, and the like, where “S” is styrene, “I” is isobutylene, and “B” is butadiene), butyl rubber, halobutyl rubber, copolymers of isobutylene and para-alkylstyrene, halogenated copolymers of isobutylene and para-alkylstyrene, copolymers of butadiene with acrylonitrile, polychloroprene, alkyl acrylate rubber, chlorinated isoprene rubber, acrylonitrile chlorinated isoprene rubber, and combinations of two or more thereof. Diene rubbers are preferred, particularly polybutadienes and mixtures of polybutadiene with other elastomers, and especially 1,4-polybutadiene having a cis-structure of at least 40%. In a particularly preferred embodiment, the rubber composition is a reaction product of a diene rubber, a crosslinking agent, a filler, a co-crosslinking agent or free radical initiator, and optionally a cis-to-trans catalyst. The rubber is preferably selected from polybutadiene and styrene-butadiene. The crosslinking agent typically includes a metal salt, such as a zinc-, aluminum-, sodium-, lithium-, nickel-, calcium-, or magnesium salt, of an unsaturated fatty acid or monocarboxylic acid, such as (meth) acrylic acid. Preferred crosslinking agents include zinc acrylate, zinc diacrylate (ZDA), zinc methacrylate, and zinc dimethacrylate (ZDMA), and mixtures thereof. The crosslinking agent is present in an amount sufficient to crosslink a portion of the chains of the polymers in the composition. The crosslinking agent is generally present in the rubber composition in an amount of from 15 to 30 phr, or from 19 to 25 phr, or from 20 to 24 phr. The desired compression may be obtained by adjusting the amount of crosslinking, which can be achieved, for example, by altering the type and amount of crosslinking agent. The free radical initiator can be any known polymerization initiator which decomposes during the cure cycle, including, but not limited to, dicumyl peroxide, 1,1-di-(t-butylperoxy) 3,3,5-trimethyl cyclohexane, a-a bis-(t-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5 di-(t-butylperoxy)hexane or di-t-butyl peroxide, and mixtures thereof. The rubber composition optionally contains one or more antioxidants. Antioxidants are compounds that can inhibit or prevent the oxidative degradation of the rubber. Suitable antioxidants include, for example, dihydroquinoline antioxidants, amine type antioxidants, and phenolic type antioxidants. The rubber composition may also contain one or more fillers to adjust the density and/or specific gravity of the core or cover. Fillers are typically polymeric or mineral particles. Exemplary fillers include precipitated hydrated silica, clay, talc, asbestos, glass fibers, aramid fibers, mica, calcium metasilicate, barium sulfate, zinc sulfide, lithopone, silicates, silicon carbide, diatomaceous earth, polyvinyl chloride, carbonates (e.g., calcium carbonate and magnesium carbonate), metals (e.g., titanium, tungsten, aluminum, bismuth, nickel, molybdenum, iron, lead, copper, boron, cobalt, beryllium, zinc, and tin), metal alloys (e.g., steel, brass, bronze, boron carbide whiskers, and tungsten carbide whiskers), metal oxides (e.g., zinc oxide, iron oxide, aluminum oxide, titanium oxide, magnesium oxide, and zirconium oxide), particulate carbonaceous materials (e.g., graphite, carbon black, cotton flock, natural bitumen, cellulose flock, and leather fiber), microballoons (e.g., glass and ceramic), fly ash, regrind, nanofillers and combinations thereof. The rubber composition may also contain one or more additives selected from free radical scavengers, accelerators, scorch retarders, coloring agents, fluorescent agents, chemical blowing and foaming agents, defoaming agents, stabilizers, softening agents, impact modifiers, plasticizers, and the like. The rubber composition may also contain a soft and fast agent, such as those disclosed in U.S. patent application Ser. No. 11/972,240, the entire disclosure of which is hereby incorporated herein by reference. Examples of commercially available polybutadienes suitable for use in forming golf ball core layers of the present invention include, but are not limited to, Buna CB23, commercially available from LANXESS Corporation; SE BR-1220, commercially available from The Dow Chemical Company; Europrene® NEOCIS ® BR 40 and BR 60, commercially available from Polimeri Europa; UBEPOL-BR® rubbers, commercially available from UBE Industries, Ltd.; and BR 01 commercially available from Japan Synthetic Rubber Co., Ltd. Suitable types and amounts of rubber, crosslinking agent, filler, co-crosslinking agent, initiator and additives are more fully described in, for example, U.S. Pat. Nos. 7,138,460, 6,939,907, and 7,041,721, and U.S. Pat. Nos. 6,566,483, 6,695,718, and 6,939,907, the entire disclosures of which are hereby incorporated herein by reference.

In embodiments of the present invention wherein at least one layer is formed from a conventional HNP composition, suitable HNP compositions comprise an HNP and optionally additives, fillers, and/or melt flow modifiers. Suitable HNPs are salts of homopolymers and copolymers of α,β-ethylenically unsaturated mono- or dicarboxylic acids, and combinations thereof, optionally including a softening monomer. The acid polymer is neutralized to 70% or higher, including up to 100%, with a suitable cation source. Suitable additives and fillers include, for example, blowing and foaming agents, optical brighteners, coloring agents, fluorescent agents, whitening agents, UV absorbers, light stabilizers, defoaming agents, processing aids, mica, talc, nanofillers, antioxidants, stabilizers, softening agents, fragrance components, plasticizers, impact modifiers, acid copolymer wax, surfactants; inorganic fillers, such as zinc oxide, titanium dioxide, tin oxide, calcium oxide, magnesium oxide, barium sulfate, zinc sulfate, calcium carbonate, zinc carbonate, barium carbonate, mica, talc, clay, silica, lead silicate, and the like; high specific gravity metal powder fillers, such as tungsten powder, molybdenum powder, and the like; regrind, i.e., core material that is ground and recycled; and nano-fillers. Suitable melt flow modifiers include, for example, fatty acids and salts thereof, polyamides, polyesters, polyacrylates, polyurethanes, polyethers, polyureas, polyhydric alcohols, and combinations thereof. Suitable HNP compositions also include blends of HNPs with partially neutralized ionomers as disclosed, for example, in U.S. Patent Application Publication No. 2006/0128904, the entire disclosure of which is hereby incorporated herein by reference, and blends of HNPs with additional thermoplastic and thermoset materials, including, but not limited to, ionomers, acid copolymers, engineering thermoplastics, fatty acid/salt-based highly neutralized polymers, polybutadienes, polyurethanes, polyesters, thermoplastic elastomers, and other conventional polymeric materials. Suitable HNP compositions are further disclosed, for example, in U.S. Pat. Nos. 6,653,382, 6,756,436, 6,777,472, 6,894,098, 6,919,393, and 6,953,820, the entire disclosures of which are hereby incorporated herein by reference.

Ionomeric compositions used to form golf ball layers of the present invention can be blended with non-ionic thermoplastic resins, particularly to manipulate product properties. Examples of suitable non-ionic thermoplastic resins include, but are not limited to, polyurethane, poly-ether-ester, poly-amide-ether, polyether-urea, Pebax® thermoplastic polyether block amides commercially available from Arkema Inc., styrene-butadiene-styrene block copolymers, styrene(ethylene-butylene)-styrene block copolymers, polyamides, polyesters, polyolefins (e.g., polyethylene, polypropylene, ethylene-propylene copolymers, ethylene-(meth)acrylate, ethylene-(meth)acrylic acid, functionalized polymers with maleic anhydride grafting, epoxidation, etc., elastomers (e.g., EPDM, metallocene-catalyzed polyethylene) and ground powders of the thermoset elastomers.

Also suitable for forming the core and core layers are the compositions having high COR when formed into solid spheres as disclosed in U.S. Pat. No. 6,953,820 and U.S. Pat. No. 6,653,382, the entire disclosures of which are hereby incorporated herein by reference. Reference is also made to U.S. Pat. No. 6,939,907, for various ball constructions and materials that can be used in golf ball core, intermediate, and cover layers. A preferable golf ball has a core having a diameter from about 0.5 to 1.25 inches and a core layer having a thickness from about 0.25 to 0.50 inches.

Additional materials suitable for forming the core layers include the core compositions disclosed in U.S. Pat. No. 7,300,364, the entire disclosure of which is hereby incorporated herein by reference. For example, suitable center and outer core materials include HNPs neutralized with organic fatty acids and salts thereof, metal cations, or a combination of both. In addition to HNPs neutralized with organic fatty acids and salts thereof, core compositions may comprise at least one rubber material having a resilience index of at least about 40. Preferably the resilience index is at least about 50. Polymers that produce resilient golf balls and, therefore, are suitable for the present invention, include but are not limited to CB23, CB22, commercially available from of Bayer Corp. of Orange, Tex., BR60, commercially available from Enichem of Italy, and 1207G, commercially available from Goodyear Corp. of Akron, Ohio. Additionally, the unvulcanized rubber, such as polybutadiene, in golf balls prepared according to the invention typically has a Mooney viscosity of between about 40 and about 80, more preferably, between about 45 and about 65, and most preferably, between about 45 and about 55. Mooney viscosity is typically measured according to ASTM-D1646.

In addition to the above materials, the center can be formed from a low deformation material selected from metal, rigid plastics, polymers reinforced with high strength organic or inorganic fillers or fibers, and blends and composites thereof. Suitable low deformation materials also include those disclosed in U.S. Pat. No. 7,004,856, the entire disclosure of which is hereby incorporated herein by reference.

While the illustrative embodiments of the invention have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those of ordinary skill in the art without departing from the spirit and scope of the invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the examples and descriptions set forth herein, but rather that the claims be construed as encompassing all of the features of patentable novelty which reside in the present invention, including all features which would be treated as equivalents thereof by those of ordinary skill in the art to which the invention pertains. 

1. A multi-layer golf ball comprising at least a casing layer, a cover, and a core, wherein the casing layer is formed from an ultra high melt flow index maleic anhydride terpolymer blended with a single high acid based ionomer wherein the terpolymer has a melt flow index of at least 70 g/10 min. at 190° C.
 2. A golf ball according to claim 1, wherein the ultra high melt flow index of the terpolymer is about 20 to 250 g/10 min. at 190° C.
 3. A golf ball according to claim 1, wherein the ultra high melt flow index of the terpolymer is about 70 to 225 g/10 min. at 190° C.
 4. A golf ball according to claim 1, wherein the ultra high melt flow index of the terpolymer is about 175 to 225 g/10 min. at 190° C.
 5. The golf ball according to claim 1, wherein the maleic anhydride terpolymer comprises a copolymer of ethylene-alkyl acrylate-maleic anhydride.
 6. The golf ball according to claim 5, wherein the alkyl acrylate is selected from the group consisting of methyl, or ethyl, or propyl, or butyl, or pentyl acrylate.
 7. The golf ball according to claim 6, wherein the alkyl acrylate in the terpolymer is ethyl acrylate.
 8. The golf ball according to claim 1, wherein the maleic anhydride terpolymer comprises about 1 to 4 wt % of maleic anhydride.
 9. The golf ball according to claim 1, wherein the maleic anhydride terpolymer has a flexural modulus in the range of 1,000 to 20,000 psi.
 10. The golf ball according to claim 1, wherein the single high acid ionomer is ethylene-acrylic or methacrylic acid and they are neutralized with a cation selected from the group consisting of lithium, sodium, magnesium, zinc, or potassium.
 11. The golf ball according to claim 10, wherein the neutralization level for the ionomer is about 30 to 70% by weight.
 12. The golf ball according to claim 10, wherein the acid content is about 16 to 25% by weight.
 13. The golf ball according to claim 1, wherein the maleic anhydride terpolymer has a melting point in the range of 65 to 108° C.
 14. The golf ball according to claim 13, wherein the maleic anhydride terpolymer has a melting point in the range of 100 to 102° C.
 15. The golf ball according to claim 1, wherein the melt flow index of the ionomer in the casing layer is about 1 to 5 g/10 min. at 190° C.
 16. The golf ball according to claim 15, wherein the melt flow index of the ionomer in the casing layer is about 2.5 to 4.5 g/10 min. at 190° C.
 17. The golf ball according to claim 1, wherein the cover is formed from a thermoset polyurethane or polyurea.
 18. The golf ball according to claim 17, wherein the cover has a thickness of 0.025 to 0.045 inch.
 19. The golf ball according to claim 1, wherein the casing layer has a thickness of 0.030 to 0.050 inch.
 20. The golf ball according to claim 1, wherein the maleic anhydride terpolymer composition in the casing layer is about 10 to 40% by weight.
 21. The golf ball according to claim 20, wherein the maleic anhydride terpolymer composition in the casing layer is about 15 to 30% by weight.
 22. The golf ball according to claim 21, wherein the maleic anhydride terpolymer composition in the casing layer is about 16 to 25% by weight.
 23. The golf ball according to claim 1, wherein the core further includes a core layer around the core.
 24. The golf ball according to claim 23, wherein the core has a diameter from about 0.5 to 1.25 inches and the core layer has a thickness from about 0.25 to 0.50 inch. 